This invention relates to char-forming aromatic polymers having reduced flame propagation characteristics.
By reason of their desirable physical properties and reasonable cost, aromatic polymers such as polystyrene and bisphenol-A polycarbonate have been used in diverse applications, e.g., as solid molding materials and as foamed compositions. Unfortunately, such polymers burn readily and continuously upon exposure to flame.
It has been a wide-spread practice to reduce the propensity of such polymers to ignite by incorporating into them various phosphorous, nitrogen and halogen-containing additives. Such additives, however, often deleteriously affect the physical properties of the aromatic polymers. In addition, these aromatic polymers, even though modified to be combustion resistant, melt or drip upon exposure to flame. As a result, a puddle of burning polymer is often formed that evolves substantial quantities of noxious fumes and smoke.
In view of the aforementioned deficiencies of conventional aromatic polymers, it would be highly desirable to provide aromatic polymer compositions which are combustion resistant and char-forming with minimum sacrifice of physical properties.